1. Field of the Invention
The present invention relates to an omnidirectional vehicle.
2. Description of the Related Art
International Publication No. WO 2008/132779 discloses an omnidirectional moving apparatus, in which a main wheel is arranged between rotating members to which a plurality of free rollers are concentrically attached and the main wheel is adapted to be movable in all directions by driving the main wheel using a lateral force of the free rollers, and an omnidirectional vehicle using the omnidirectional moving apparatus.
In addition, International Publication No. WO 2008/139740 discloses an omnidirectional vehicle (a conveyance) having sub wheels (auxiliary wheels) each of which is able to contact with the ground at a position apart from the ground contact point of a main wheel (traveling drive wheel) which is able to be driven in all directions so as to be able to turn in a small turning radius. The sub wheel is rotatably attached to the rear end of an arm which is pivotally supported by a bracket attached to the rear surface of the vehicle body.
The sub wheel is, for example, an omni-wheel able to be driven by an electric motor. In this case, the vehicle is able to be rotated with the ground contact point of the main wheel as the center. Furthermore, it is possible to select a grounded state or an ungrounded state of the sub wheel whether the arm is flipped up by manipulation of a handlebar.
In the omnidirectional vehicle disclosed in International Publication No. WO 2008/139740, however, the traction of the sub wheel becomes unstable particularly when the vehicle body largely inclines in the anteroposterior direction. Furthermore, the grounded state and the ungrounded state of the sub wheel is changed by passenger's manipulation, and therefore the passenger is likely to be unsuccessful in performing a moving operation such as a turn intended by the passenger by erroneous manipulation.
The present invention has been made in view of the above background. Therefore, it is an object of the present invention to provide an omnidirectional vehicle which is stable in the traction of sub wheels.